Musculoskeletal disorders or (MSD) are forms of injuries affecting connective tissue such as muscles, nerves, joints, cartilage and spinal discs (Bureau of Labor Statistics, 2008). Some estimates state that 70% of all people will experience neck and shoulder pain though out their lives due to sedentary behavior and Work Related Musculoskeletal Disorders (WMSD). This pain occurs in individuals who hold certain postures for prolonged periods of time which in turn affects their neck and shoulder muscles as there is too much tension on these muscle groups. These injuries may occur when muscles or tendons are either over-used or stretched past their capabilities. Ergonomic risk factors such as repetitive motion, awkward posture, forceful exertions, pressure points, and static postures can cause or worsen MSD (NIOSH, 2007). For example, repetitive strain injury (such as carpal tunnel syndrome, and tendinitis) of the wrist and arm have risen by 80% since 1990 according to the US bureau of Statistics, and are now the single largest cause of work related injury. This is being described as the epidemic of the nineties. In the US alone, more than 600,000 workers have MSD resulting in days away from work each year (Bureau of Labor Statistics, U.S. Department of Labor, (2001). MSDs impact Canadian society by costing the health care system $20 billion (McGee et al., 2007).
Long periods of using a computer at work settings have been shown to cause musculoskeletal discomfort and mood disturbances; however, active or passive stretches have been shown to decrease the incidence of such disturbances (Sundelin et al. 1986, Zwahlen and Adams 1987, Swanson et al. 1989, Carter and Banister 1994, Hales et al. 1994). Frequent stretches can also reduce static loads on the musculoskeletal system including the muscles and the spine (Sundelin and Hagberg 1989).
Electromyographic studies were conducted by Anderson (1984) to measure muscle activation in a set of office workers using surface electrodes which were placed strategically on various muscles in the neck/shoulder and back. Results demonstrated that certain muscles, like the upper trapezius muscle, were highly activated during 90 degree elevation of the shoulder joint (Anderson, 1984). A possible reason for this could be that computer workers postures are poor due to slouching over their computers with elevation of the arms due to typing on the keyboard all day. This may result in specific back muscles being overly activated and reaching peak force when constantly stimulated. Active or passive stretching may lower the peak force and rate of firing and therefore take pressure away from these muscles.
Stretching, whether active or passive, is a form of physical activity in which skeletal muscles are lengthened to improve muscles elasticity and reduce tensile stress (Knudson et al. 2000; Harvey et al., 2002; Shrier, 2004; Decoster et al., 2005). The benefits of stretching include increased flexibility, improved range of motion within joints, improved circulation improved posture, and stress relief (Magnusson and Renstrom, 1998). In biomechanics terms, flexibility is the ability to change muscle tendon length which is brought about by viscoelastic properties (Sharman, Melanie, Cresswell, Riek. 2006). Viscoelasticity is a measure of a tissue's ability to deform or change length when a load is applied to it over time and to resume its original size and shape when the force is removed, much like stretching and releasing a rubber band (Sharman et al., 2006).
Active or passive stretching increases the distance a tissue can stretch as well as the force required to tear the muscle tendon unit, making injury less likely. The presumption is that, for individuals with short or “tight” muscles, stretching increases flexibility by elongating muscle fibers to a more physiologically normal range, promoting optimal function and reducing the risk of musculoskeletal injury.
Several research studies have shown that stretching as mentioned results in elongation of the muscle tendon unit, as well as reductions in peak force and rate of force production, therefore making the muscle tendon less stiff (Knudson et al., 2000; Harvey et al. 2002; Guissard and Duchateau, 2004; Decoster et al. 2005). This increases the distance a tissue can stretch as well as the force required to tear it; thus onset of injury is reduced. The presumption is that if muscles are tight (i.e. shorter in length) then chances of injury may increase. In fact, most sedentary individuals that have tight muscles suffer from pain in the neck and shoulder region due to not stretching their neck and shoulder muscles.
A study by the National Institute of Occupational Safety and Health (NIOSH) and the Internal Revenue Service (IRS) examined the symptoms and performance of data-entry workers. Participants from the Cincinnati IRS Service Center were sampled for analyses. The data sample included 47 women and 4 men, aged 23-60 years, with a mean age of 36 years. Data-entry experience ranged from 1 month to 24 years, with a mean of 6 years. One group had rest breaks along with stretch exercise breaks and the control group did not do either. The stretch exercise breaks were organized as follows: 4 weeks (two 15 min breaks/day); 4 weeks with supplementary breaks (two 15 min breaks plus four 5 min breaks/day). A questionnaire was then filled out by both groups of workers and it was reported that the workers in the rest/exercise break group only participated in 25% of conventional rest breaks and 39% of supplementary stretch exercise breaks. The study did not find any major conclusion of stretching and discomfort or performance. This was due to low compliance and low participation rates to perform the stretches as mentioned by Galinsky, Swanson, Sauter, Dunkin, Hurrell, & Schleifer, (2007). This low compliance may be attributed to a lack of motivation to do the stretches actively. However the individuals who did perform the stretches had lower discomfort and lower eyestrain during their work sessions. Also, the efficiency of these workers was significantly faster in data-entry speed at work and they made up for the 20 minute breaks by producing better output. Trujillo & Zeng (2006) from East Carolina University observed the effectiveness of a computer-based stretch program that notified the computer user to stop and stretch in the hope of offsetting musculoskeletal disorders. The computer-based stretch program demonstrated that the stretches helped relax tense muscles, improve blood circulation, increase the person's Range of Motion (ROM) and prevent cumulative trauma disorders.
There have been efforts to reduce the risk factors for MSD including ergonomic engineering and active stretch programs but the compliance rate and participation rate, as research indicates, is very low most commonly due to a lack of motivation.